Horse Liver Alcohol Dehydrogenase

作者：Hans Jörnvall, J. Ieuan Harris · 发表于：European Journal of Biochemistry · 年份：1970 · DOI：10.1111/j.1432-1033.1970.tb00962.x · 被引用次数：98 · 研究领域：Alcohol Consumption and Health Effects、Muscle metabolism and nutrition、Biochemical effects in animals

The ethanol‐active isoenzyme of alcohol dehydrogenase from horse liver has been carboxy‐methylated with iodo[2‐14C]acetate in 6 M guanidine hydrochloride. A study of the tryptic digest of the carboxymethylated enzyme has shown that it contains 14 unique sequences with [2‐14C]‐carboxymethylcysteine, two with tryptophan, one with C‐terminal phenylalanine and one with a blocked N‐terminal residue which represents the N‐terminal sequence in the protein chain. This number of unique residues found in peptides is in each case half the number previously found by direct amino acid analysis (based on a molecular weight of 80000) of the intact enzyme. These results support the view that the native isoenzyme is a dimer consisting of two similar and probably identical polypeptide chains each containing about 370 amino acid residues. Failure to demonstrate the presence of more than one type of chain by chromatography of the carboxymethylated enzyme on DEAE‐cellulose provides additional support for the dimer hypothesis. An alternative proposal [13] that the enzyme is composed of two pairs of dissimilar chains each with a molecular weight of 20000 appears to be incompatible with these results.